There are many different ways in which a note can be sung or played, e.g., loud, soft, staccato, legato, etc. These are referred to as articulations. The way you articulate notes can make a dramatic difference to the way the music sounds.
In written music specific markings indicate the articulation desired by the composer. Two examples of this are shown next. For example, a short horizontal line directly above or below a note indicates that the note is to be held for its full written duration. This articulation is referred to as tenuto. Another common articulation which you may already know is staccato, which means the note is to be short and separate from other notes. Staccato is indicated by a dot directly above or below a note.
Listen to the recording to hear the effect produced by tenuto and staccato in this example. Experiment with these articulations by applying them to phrases you already know well and then try improvising with them. It is also important to listen to albums featuring your favorite singers. Pay careful attention to how they articulate notes in different styles and situations. If you do this for even a few minutes each day, you will soon begin to instinctively know how to articulate notes yourself.